understood as a consequence of two operations. The first is the (± 1)-

This can be understood as a consequence of two operations. The first is the (± 1)- averaging having more +1 value over a window size of the image itself. This leads naturally to a low pass blurred image ne ar the 1/2 gray scale value. This is obtained by Eqs(16,lb) (ui =Lj W ij(t2:16) X(Pj) =L'j X(Pj)). The second operation (vi=crN(ui)) occurs near the part of the sigmoidal curve associated with gray values about 1/2. Occasionally (when ui<1), some pixels which are darker than 1/2 are reversed by the negative logic.